1. Field of the Invention
The present invention relates to liquid containers for storing liquids for use in inkjet recording. Examples of the liquids include an ink containing a coloring material, such as a dye or pigment, and a functional liquid for enhancing characteristics of printing results. The present invention further relates to liquid containers for storing liquids (including an ink) not only for use in inkjet recording but for various recording apparatuses.
The present invention is applicable to liquid containers for general printing apparatuses, copiers, facsimiles having a communication system, word processors having a printing unit, and industrial recording apparatuses compositely combined with various processing apparatuses.
2. Description of the Related Art
A known type of inkjet recording apparatus includes an inkjet head, an ink tank connected to the inkjet head and storing ink to be ejected, and a carriage on which the inkjet head and the ink tank are mountable. For recording, the inkjet recording apparatus ejects ink droplets from fine nozzles of the inkjet head onto a recording medium while causing the carriage and the recording medium to move relative to each other, thereby achieving desired recording.
An ink tank for such a recording apparatus (printer) has a negative pressure generating mechanism for generating a negative pressure for the inkjet head. The negative pressure generated by the negative pressure generating mechanism is sufficiently high to balance with a retaining force of an ink meniscus formed at an ink ejecting part of the inkjet head, and thus to prevent ink leakage from the ink ejecting part. The negative pressure is set at a level which allows a sufficient supply of ink for an ink ejecting operation of the inkjet head.
An example of the negative pressure generating mechanism is one in which a porous or fibrous member to be impregnated with ink is disposed in the ink tank so that an appropriate negative pressure is generated by an ink retaining force of the porous or fibrous member. Another example of the negative pressure generating mechanism is one in which an ink containing bag is formed of an elastic member (e.g., rubber member) having tension in a direction in which the volume of the ink containing bag increases and thus, a negative pressure is applied to ink by drag resulting from deformation of the elastic member caused by ink consumption. Still another example of the negative pressure generating mechanism is one in which a bag-like member is formed of a flexible film (flexible sheet body), an elastic structure (e.g., spring) capable of biasing the bag-like member in a direction in which the capacity of the bag-like member increases is disposed inside or outside the bag-like member, and thus a negative pressure is generated (see, e.g., U.S. Pat. No. 6,250,751).
As an example of the configuration of the ink tank formed of a flexible film and having a spring member as a mechanism for generating a negative pressure, a configuration disclosed in Japanese Patent Laid-Open No. 2007-062335 is also known. The disclosed configuration of the ink tank will be described with reference to FIG. 10.
FIG. 10 is a cross-sectional view schematically illustrating a configuration of an ink tank. The ink tank of FIG. 10 has a thin flat main body having one wall (first wall), the other wall (second wall) opposite the first wall, and a side wall connecting the first and second walls. The main body includes a housing 5 and a lid member 4. The housing 5 has an opening on the first wall's side and a supply port for leading out liquid (ink) from inside. The lid member 4 is joined to the opening of the housing 5 and has an air communication port 21. A flexible member 3 joined to the opening of the housing 5 is disposed inside the ink tank. The flexible member 3 and the second wall of the main body define a space for storing ink therebetween. A spring member 1 for generating a negative pressure and a plate member 2 are disposed in the space defined by the housing 5 and the flexible member 3. The plate member 2 is disposed between the flexible member 3 and the spring member 1. The lid member 4 is integral with a rib 7 for regulating movement of the plate member 2 displaced in accordance with ink consumption.
In the ink tank of this type, it is desirable that the flexible member 3 and the housing 5 be made of the same polymer material. An enclosed structure, except for the supply port, of the ink tank is thus formed by thermal welding. An opening of the supply port is one for generating a meniscus force which does not allow air to be taken in by negative pressure from the spring member 1. For example, a mesh filter having such a meniscus force is secured to the opening of the supply port.
The plate member 2 disposed between the spring member 1 and the flexible member 3 is in contact with the flexible member 3 in a large area. This allows stable displacement of the flexible member 3. The spring member 1 and the plate member 2 are secured to each other by swaging, welding, or the like to prevent positional displacement therebetween.
The ink tank having the above-described configuration is mounted onto a printer in a direction orthogonal to the biasing direction of the spring member 1 such that the supply port faces downward during use (i.e., in the direction of gravity indicated by arrow “g” of FIG. 10). Therefore, the plate member 2 is affected by gravity. Additionally, since the ink tank is mounted on a carriage, the ink tank undergoes acceleration in the direction of carriage travel during printing, due to return of the carriage or the like. As a result, the plate member 2 is easily moved by scanning of the carriage and thus becomes unstable.
After being molded to a predetermined shape, the flexible member 3 is welded to the opening of the housing 5. Since the flexible member 3 tends to be easily displaced, the predetermined shape of the flexible member 3 becomes unstable due to an increase or decrease in pressure inside the ink chamber 9 during manufacture, or due to vibration or drop during transport.
The negative pressure in the ink tank is generated by an elastic force of the spring member 1 through the plate member 2. If the shape of the flexible member 3 is unstable or the plate member 2 is displaced, it is difficult to keep the elastic force of the spring member 1 constant. This can cause an unstable internal pressure (negative pressure) in the ink tank. To achieve a stable negative pressure, it is necessary that the flexible member 3 be of a predetermined shape and the plate member 2 be located at a predetermined position. For example, to regulate the position of the plate member 2, the rib 7 integral with the lid member 4 is disposed around the periphery of the plate member 2. With the rib 7, the position of the plate member 2 can be regulated, the shape of the flexible member 3 can be stabilized, and thus a stable negative pressure can be maintained when the ink tank is mounted on the printer and printing is performed.
In the ink tank having a negative pressure generating mechanism realized by the flexible member 3, the plate member 2, and the spring member 1, there is provided a clearance between the rib 7 and the plate member 2 for manufacturability and stable movement of the plate member 2 associated with ink consumption.
U.S. Pat. No. 6,250,751 discloses a configuration in which a rib for regulating a plate member is integral with a housing and is provided around the entire periphery of the plate member. A flexible member is molded to substantially the same shape as the plate member. There is a clearance between the rib and the plate member. The flexible member between the plate member and the rib is caught by them when the plate member is moved by an external force applied to the ink tank. In this disclosed example, the flexible member is a thin film having a thickness as very small as about 30 to 100 μm. It is thus likely that the thin film caught between the plate member and the rib will be broken.
Japanese Patent Laid-Open No. 2007-062335 discloses a method in which, to reduce a force applied to a flexible member (film), the area of contact between a plate member and the flexible member is increased. To increase this area of contact, the outer edge of a plate member made of metal is bent at an obtuse angle or the shape of a plate member made of polymer is changed to form a curved surface. Additionally, there is disclosed a method in which shock caused by contact between a flexible film and a rib is reduced. To achieve this, the area of a part of the flexible film, the part on which a plate member is disposed, is made larger than the area of the plate member. Moreover, there is disclosed a method in which a part of a rib, the part with which a plate member strongly interferes, is shaped to avoid interference in a limited area.
The above-described methods are widely applicable regardless of the volume of the ink tank, and make it possible to reduce impact force and avoid collision in a limited area. However, in a configuration where the volume of ink is increased, a further improvement is desired because an increase in weight may cause unexpected problems if the ink tank is dropped or vibrated.
As for a configuration of an ink tank including an ink bag, Japanese Patent Laid-Open No. 2002-355988 discloses a means for preventing pressure changes in the ink bag caused by shaking during printing operation. In this disclosed example, since the ink bag has no negative pressure generating mechanism (including a spring and a plate member) therein, the ink bag is moved significantly by an inertial force of ink during printing operation. As a means for avoiding this, a plate member is placed over the entire area of the outer upper part of the ink bag such that the outer edge of the plate member is in contact with the inner wall of a container containing the ink bag. With this configuration, the plate member placed over the entire upper part of the ink bag can suppress movement of the ink bag. However, since the plate member is only placed on the ink bag, if an external pressure is applied to the ink tank, for example, due to vibration, drop, or the like during transport, the weight of the plate member may directly act on the entire ink bag. This may cause an increase in pressure inside the ink bag and lead to ink leakage from a supply port or the like.